Liquid crystal display having a particular arrangement of pixel electrodes

ABSTRACT

A liquid crystal display includes a first insulating substrate, and a second insulating substrate facing the first insulating substrate. Gate lines are formed on the first insulating substrate while extending in a horizontal direction. A gate insulating layer is formed on the gate lines. A semiconductor layer and data lines are formed on the gate insulating layer. The data lines extend in a vertical direction. Source electrodes are formed on the semiconductor layer while being connected to the data lines. Drain electrodes face the source electrodes. A protective layer is formed on the data lines, and pixel electrodes are formed on the protective layer such that the pixel electrodes are connected to the drain electrodes while having a plurality of slits and horizontal opening portions. A common electrode is formed on the second insulating substrate with a plurality of opening portions. The horizontal opening portions of the pixel electrode and the opening portions of the common electrode partition the pixel region into left and right domains as well as upper and lower domains. The slits are positioned at the left and right domains.

CROSS-REFERENCE TO RELATED UNITED STATES APPLICATION

This application is a continuation of, and claims priority from, U.S.patent application Ser. No. 10/205,326, of Jang-Kun Song, filed on Jul.25, 2002 now U.S. Pat. No. 7,460,191.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a liquid crystal display, and moreparticularly, to a liquid crystal display for widening a viewing angle.

(b) Description of the Related Art

Generally, a liquid crystal display has two panels with electrodes, anda liquid crystal layer interposed between the two panels. Voltages areapplied to the electrodes so that the liquid crystal molecules in theliquid crystal layer are re-oriented to thereby control lighttransmission.

Liquid crystal displays are widely used because they exhibit excellentdisplay characteristics, but they do have a major shortcoming when theirviewing angle is narrow. Various techniques for widening the viewingangle have been developed. For instance, liquid crystal molecules may bealigned perpendicular to top and the bottom panels while forming apredetermined pattern of openings or protrusions at a pixel electrodeand a common electrode.

In the case of formation of the opening pattern, the liquid crystalmolecules are controlled in orientation by way of a fringe field due tothe opening pattern formed at the pixel electrodes and/or the commonelectrode.

In the case of formation of the protrusion pattern, protrusions areformed at the pixel electrode and/or the common electrode, and theliquid crystal molecules are controlled in orientation by way ofelectric field deformed due to the protrusion pattern.

Furthermore, it is proposed that an opening pattern is formed at thepixel electrode while forming a protrusion pattern at the commonelectrode. The liquid crystal molecules are controlled in orientation byway of the fringe field due to the opening pattern and the protrusionpattern while forming a plurality of domains.

In such a multi-domain liquid crystal display, the viewing angle percontrast ratio of 1:10 or the viewing angle defined as the limit angleof the inter-gray scale brightness inversion reaches 80 or more in alldirections. However, if the lateral gamma curve is deviated from thefront gamma curve, visibility at left and right sides is deteriorated,even when compared to the twisted nematic (TN) mode liquid crystaldisplay. For instance, in a patterned vertically aligned (PVA) modewhere opening portions are formed for the domain partitioning, thedisplay becomes much brighter as it comes to the lateral side, and thecolor becomes white. In a serious case, the bright gray scales areremoved while conglomerating the picture images. Thus, it is desirableto reduce deterioration of colors on the left and right sides, therebyenhancing the image quality of an LCD.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, the liquid crystaldisplay has a plurality of pixel regions. Each pixel region has aplurality of micro domains. The micro domains include a firstdirectional domain and a second directional domain having differentaverage inclination directions of liquid crystal molecules when electricfield is applied. The electric field within the first directional domainis weaker than the electric field within the second directional domain.

When viewed from a front side, the liquid crystal molecules in the firstdirectional domain are inclined left and right while the liquid crystalmolecules in the second directional domain are inclined up and down. Thepredetermined is value of difference in the electric field between thefirst directional domain and the second directional domain ranges fromabout 0.02/d (V/μm) to about 0.5/d (V/μm) where d is a cell gap (μm).

According to another aspect of the present invention, the liquid crystaldisplay has a first insulating substrate, and a first signal line formedon the first insulating substrate in a first direction. A second signalline is formed on the first insulating substrate in a second directionwhile intersecting the first signal line in an insulating manner. Afirst thin film transistor is connected to the first and the secondsignal lines. A second thin film transistor is connected to the firstand the second signal lines. A first pixel electrode is connected to thefirst thin film transistor. A second pixel electrode is connected to thesecond thin film transistor. A second insulating substrate faces thefirst insulating substrate. A common electrode is formed on the secondinsulating substrate. A liquid crystal layer is interposed between thefirst and the second substrates. A domain partitioning member is formedon at least one of the first and the second insulating substrates whilepartitioning the first and the second pixel electrodes into a pluralityof micro domains. The domain partitioning member partitions the firstand the second pixel electrodes into first directional domains andsecond directional domains, and the first and the second pixelelectrodes are connected through a capacitor.

The first and the second thin film transistors at a pixel of an nthpixel row and an m-th pixel column are connected to an m-th data line,and the first and the second thin film transistors at a pixel of an(n+1)-th pixel row and the m-th pixel column are connected to an(m+1)-th data line wherein n and m are integers. The second pixelelectrode occupies the first and second pixel electrode by about 30-70%.The liquid crystal molecules in the liquid crystal layer are verticallyaligned with respect to the first and the second insulating substratesin absence of an electric field.

A storage capacitor line is further formed on the first insulatingsubstrate while being placed between the first pixel electrode and thesecond pixel electrode to thereby form a storage capacitor. When aliquid crystal capacitance formed between the second pixel electrode anda common electrode is indicated by Clcb, a storage capacitance formedbetween the second pixel electrode and the storage capacitor line isindicated by Cstb, and a connection capacitance formed between the firstand the second pixel electrodes is indicated by Cpp, a value of Tdefined by the equation T=(Clcb+Cstb−Cpp)/(Clcb+Cstb+Cpp) is in therange of about 0.65-0.95.

According to still another aspect of the present invention, the liquidcrystal display has a first insulating substrate, and a first signalline formed at the first insulating substrate in a first direction. Asecond signal line is formed at the first insulating substrate in asecond direction while crossing over the first signal line. A thin filmtransistor is connected to the first and the second signal lines. Apixel electrode is connected to the thin film transistor. A secondinsulating substrate faces the first insulating substrate. A commonelectrode is formed at the second insulating substrate. A liquid crystallayer is interposed between the first and the second substrates. Adomain partitioning member is formed on at least one of the first andthe second insulating substrates while partitioning the pixel electrodeinto a plurality of micro domains. The domain partitioning memberpartitions the pixel electrode into first directional domains and seconddirectional domains, and the first directional domains includes aplurality of slits.

A width of the slit is about 2-5 μm and the distance between theneighboring two slits is established to be 2-10 μm. When electric fieldis applied to the liquid crystal display, the electric field applied tothe first directional domain is weaker than the electric field appliedto the second directional domain. A difference in the electric fieldbetween the first directional domain and the second directional domainranges from about 0.02/d (V/μm) to about 0.5/d (V/μm), wherein d is acell gap (μm). The plurality of micro domains are formed by overlappingthe common electrode having a plurality of opening portions and thepixel electrode, wherein the pixel electrode comprises a plurality ofelectrode portions. Polarizing plates are further comprised, which areattached to outer surfaces of the first insulating substrate and thesecond insulating substrate.

According to still another aspect of the present invention, the liquidcrystal display has a first insulating substrate, and a first signalline formed at the first insulating substrate in a first direction. Asecond signal line is formed at the first insulating substrate in asecond direction while crossing the first signal line in an insulatingmanner. A thin film transistor is connected to the first and the secondsignal lines. A pixel electrode is connected to the thin filmtransistor. A second insulating substrate faces the first insulatingsubstrate. A common electrode is formed at the second insulatingsubstrate. A dielectric layer is formed on at least one of the pixelelectrode and the common electrode. A liquid crystal layer is interposedbetween the first and the second substrates. A domain partitioningmember is formed on at least one of the first and the second insulatingsubstrates while partitioning the pixel electrode into a plurality ofmicro domains. The domain partitioning member partitions the pixelelectrode into first directional domains and second directional domains,and the dielectric layer is placed on the first directional domains.

A thickness of the dielectric layer is about 500 Å-1.5 μm. A pluralityof opening portions are formed at the pixel electrode and the commonelectrode as the domain partitioning member.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendantadvantages thereof, will be readily apparent as the same becomes betterunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings in which likereference symbols indicate the same or the similar components, wherein:

FIG. 1 is a plan view of a liquid crystal display according to a firstpreferred embodiment of the present invention;

FIG. 2 is a cross sectional view of the liquid crystal display takenalong the line of FIG. 1;

FIG. 3 is a graph illustrating gamma curves at a front and a 60° lateralsides of the test cell;

FIG. 4 illustrates VT (Voltage-Transmittance) curves when asingle-domain vertically aligned (VA) liquid crystal cell is viewed fromeight directions;

FIG. 5 illustrates a VT curve at the front of a single-domain VA liquidcrystal cell where rubbing is vertically made in an anti-parallelmanner, an average VT curve at left and right 60° sides thereof, anaverage VT curve at top and bottom 60° sides thereof, and a moved curveof the top and bottom average curve by 0.3V;

FIG. 6 is a plan view of a liquid crystal display according to a secondpreferred embodiment of the present invention;

FIG. 7 is a cross sectional view of the liquid crystal display takenalong the VII-VII′ line of FIG. 6;

FIG. 8 is a cross sectional view of a liquid crystal display accordingto a third preferred embodiment of the present invention;

FIG. 9 is a plan view of a liquid crystal display according to a fourthpreferred embodiment of the present invention;

FIGS. 10 and 11 are cross sectional views of the liquid crystal displaytaken along the XI-XI′ line and the XII-XII′ line of FIG. 9;

FIG. 12 is an equation circuit diagram of a liquid crystal display withthe thin film transistor array panel shown in FIG. 9;

FIG. 13 is a plan view of a liquid crystal display according to a fifthpreferred embodiment of the present invention; and

FIG. 14 is an equation circuit diagram of a liquid crystal display withthe thin film transistor array panel shown in FIG. 13.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of this invention will be explained with referenceto the accompanying drawings.

FIG. 1 is a plan view of a liquid crystal display according to a firstpreferred embodiment of the present invention, and FIG. 2 is a crosssectional view of the liquid crystal display taken along the II-II′ lineof FIG. 1.

Referring to FIGS. 1 and 2, the liquid crystal display includes a thinfilm transistor array panel having a transparent insulating substrate10, a color filter panel having a transparent glass substrate 100, andliquid crystal material 900 disposed between the thin film transistorarray panel and the color filter panel.

First, the thin film transistor array panel for the liquid crystaldisplay will be explained in detail.

Gate lines 20 are formed on a transparent insulating substrate 10 suchas a glass while extending in the horizontal direction. Storagecapacitor lines 30 extend parallel to the gate lines 20. Gate electrodes21 protrude from the gate lines 20. First to fourth storage capacitorelectrodes 31-34 and storage capacitor electrode connectors 35 and 36are branched from the storage capacitor lines 30. The first storagecapacitor electrode 31 is directly connected to the storage capacitorline 30 while extending in the vertical direction. The second and thethird storage capacitor electrodes 32 and 33 are connected to the firststorage capacitor electrode 31 while extending in the horizontaldirection. The fourth storage capacitor electrode 34 is connected to thesecond and the third storage capacitor electrodes 32 and 33 whileextending in the vertical direction. The storage capacitor electrodeconnectors 35 and 36 connect the fourth storage capacitor electrode 34to the first storage capacitor electrode 31 at the pixel adjacentthereto. A gate insulating layer 40 is formed on the gate lines 20, thegate electrodes 21, the storage capacitor lines 30, the first to fourthstorage capacitor electrodes 31-34, and the storage capacitor electrodeconnectors 35 and 36, and a semiconductor layer 50 made of amorphoussilicon is formed on the gate insulating layer 40 over the gateelectrodes 21. Ohmic contact layers 61 and 62 made of amorphous silicondoped with n-type high concentration impurities such as phosphorous P isformed on the semiconductor layer 50. Source and drain electrodes 71 and72 are formed on the ohmic contact layers 61 and 62, respectively.

Data lines 70 are formed on the gate insulating layer 40 while extendingin the vertical direction. The source electrodes 71 are connected to thedata lines 70. A protective layer 80 is formed on the data lines 70, andsource and drain electrodes 71 and 72 with contact holes 81 exposing thedrain electrodes 72. A pixel electrode 90 is formed on the protectivelayer 80 at each pixel area while being connected to the drain electrode72 through the contact hole 81. The pixel electrode 90 is formed withtransparent conductive material such as indium tin oxide (ITO) andindium zinc oxide (IZO). Each pixel area is defined by the two gatelines 20 and the two data lines 70 while being partitioned into upperand lower half parts.

The pixel electrode 90 is separated into first to third electrodeportions 91-93, which are connected to each other through first to thirdconnectors 94-96. The first electrode portion 91 is located at asubstantially lower half part of the pixel area, and has a substantiallyrectangular shape where the four edges thereof are cut off. The firstelectrode portion 91 is directly connected to the drain electrode 72through the contact hole 81. The second and the third electrode portions92 and 93 are located at a substantially upper half part of the pixelarea, and have a substantially rectangular shape with the four chamferedcorners. The second electrode portion 92 is connected to the firstelectrode portion 91 through the first and the second connectors 94 and96, and the third electrode portion 93 is connected to the secondelectrode portion 92 through the third connector 95.

According to an embodiment of the present invention, a plurality ofslits 99 are formed at the first electrode portion 91. The electricfield generated between the first electrode portion 91 and a commonelectrode 400 of the color filter panel due to the slits 99 is eakerthan that generated between the common electrode 400 and the secondelectrode portion 92 or the third electrode portion 93.

Meanwhile, the second storage capacitor electrode 32 is placed betweenthe second electrode portion 92 and the third electrode portion 93, andthe third storage capacitor electrode 33 is placed between the secondelectrode portion 92 and the first electrode portion 91. The firststorage capacitor electrode 31 and the fourth storage capacitorelectrode 34 are placed between the pixel electrode 90 and the data line70. The side of the first electrode portion 91 extending parallel to thedata line is longer than the side thereof extending parallel to the gateline. The side of the second and the third electrode portions extendingparallel to the data line is shorter than the side thereof extendingparallel to the gate line. The second and the third electrode portions92 and 93 overlap the first and the fourth storage capacitor electrodes31 and 34, but the first electrode portion 91 does not overlap the firstand the fourth storage capacitor electrodes 31 and 34. The storagecapacitor line 30 is placed between the gate line 20 and the thirdelectrode portion 93. The electric potential to be applied to the commonelectrode 400 for the color filter panel is usually applied to thestorage capacitor line 30, the storage capacitor electrodes 31-34, andthe storage capacitor electrode connectors 35 and 36.

As described above, when the storage capacitor line 30 or the storagecapacitor electrodes 31-34 to be applied with the common electricpotential is placed between the data line 70 and the pixel electrode 90,or between the gate line 20 and the pixel electrode 90, the affection ofthe data line electric potential and the gate line electric potential tothe electric field of the pixel region is intercepted by the storagecapacitor line 30 and the storage capacitor electrodes 31-34, therebyforming stable domains.

The color filter panel for the liquid crystal display will be nowexplained in detail.

A black matrix 200 is formed on a transparent glass substrate 100 with adouble-layered structure while defining the pixel areas. Thedouble-layered structure for the black matrix 200 is formed withchrome/chrome oxide. A color filter 300 is formed at each pixel area,and a common electrode 400 is formed on the entire surface of thesubstrate 100 having the color filters 300 with a transparent conductivematerial. The common electrode 400 is provided with an opening patternat each pixel area. The opening pattern includes first to third openingportions 510, 520, and 530. The first opening portion 510 bisects thelower half part of the pixel region in the vertical direction, and thesecond and the third opening portions 520 and 530 trisect the upper halfpart of the pixel region in the horizontal direction. Both ends of therespective opening portions 510, 520 and 530 are gradually enlargedwhile forming the shape of a triangle. The opening portions 510, 520,and 530 are separated from each other.

Alternatively, the black matrix may be formed with an organic material,and the color filters may be formed at the thin film transistor arraypanel.

The thin film transistor array panel and the color filter panel arealigned, and assembled with each other. Liquid crystal material 900 isinjected between the two panels such that the directors of the liquidcrystal molecules are aligned perpendicular to the panels. The twopolarizing plates 11 and 101 are attached to the outer surfaces of thesubstrates 10 and 100, respectively, such that the polarizing axesthereof extend perpendicular to each other.

The electrode portions 91, 92 and 93 of the pixel electrode 90 at thethin film transistor array panel, and the first to third openingportions 510, 520, and 530 of the common electrode 400 at the colorfilter panel overlap each other to thereby partition the pixel regioninto a plurality of micro-domains. The micro-domains partitioned by thefirst electrode portion 91 and the first opening portion 510 arereferred to as left and right domains (extending in a verticaldirection), and the micro-domains partitioned by the second and thirdelectrode portions 92 and 93 and the second and third opening portions520 and 530 are referred to as upper and lower domains (extending in ahorizontal direction). This distinction is made depending upon theinclination directions of the liquid crystal molecules when electricfield is applied. The respective electrode portions 91-93 includes twolong sides and two short sides. The long side of the each electrodeportion extends parallel to the data line 70 or the gate line 20, andmakes an angle of about 45° with respect to the polarizing axis of thepolarizing plate (as shown in FIG. 1). In case the long side of therespective electrode portions 91-93 of the pixel electrode 90 ispositioned close to the data line 70 or the gate line 20, the storagecapacitor line 30 or the storage capacitor electrodes 31-34 are arrangedbetween the data line 70 and the long side of the relevant electrodeportion or the gate line 20 and the long side of the relevant electrodeportion.

According to an embodiment of the present invention, it is preferablethat the storage capacitor line 30 and the first to fourth storagecapacitor electrode 31-34 are not positioned close to the short side ofthe electrode portions 91-93 of the pixel electrode 90. When the storagecapacitor line 30 and the first to fourth storage capacitor electrode31-34 are positioned closer, it is preferably completely covered by thepixel electrode 90, or positioned distant from the pixel electrode 90 byabout 3 μm or more. The reason is that the electric potential of thedata line 70 or the gate line 20 operates in the direction of hinderingthe domain formation at the area where the data line 70 or the gate line20 is positioned close to the long side of the pixel electrode portions91-93. On the contrary, the electric potential of the data line 70 orthe gate line 20 operates in the direction of exerting the domainformation at the area where the data line 70 or the gate line 20 ispositioned close to the short side of the pixel electrode portions91-93.

Meanwhile, the electric field formed within the left and right domainsdue to the slit 99 at the first pixel electrode portions 91 is weakerthan that formed within the upper and lower domains by a predetermineddegree. With this structure, the visibility of the liquid crystaldisplay at the left and the right sides can be improved. When the cellgap of the liquid crystal display is indicated by d (μm) the electricfield formed within the left and right domains preferably generates avalue of from about 0.02/d (V/μm) to about 0.5/d (V/μm), which is weakerthan the electric field formed within the upper and lower domains. Thatis, the voltage difference between the common electrode and the pixelelectrode is established such that the voltage at the left and rightdomains is weaker than that at the upper and lower domains by about 0.1Vto about 1V. For this purpose, the width of the slit 99 is preferablyestablished to be about 2 μm to 5 μm, and the distance between theneighboring two slits 99 is established to be about 2 μm to about 10 μm.

FIG. 3 is a graph illustrating gamma curves at the front and 60°-lateralsides of a test cell.

As shown in FIG. 3, the gamma curve at the 60°-lateral side of the testcell turns out to be higher than the gamma curve at the front sidethereof. Particularly, as the width between the front side gamma curveand the lateral side gamma curve is significantly great, the brightnessdifference of two times to ten times is depended upon whether the samegray scale is viewed from the front side or from the lateral side.

According to an embodiment of the present invention, as the gray scalesof red, green, and blue pixels are separately varied, the deformationdegree in the gamma curve at the lateral side is differentiated at thered, green and blue pixels. Therefore, when viewed from the lateralside, the pixels seem to have a different color compared with beingviewed from the front side. For instance, as shown in FIG. 5, assumingthat the red, green and blue pixels express 56 gray scales, 48 grayscales, and 24 gray scales, when viewed from the front side, the ratioof the red, green and blue colors is: R:G:B=73:50:10=55%:37%:18% Bycontraries, when viewed from the 60°-lateral side, the ratio of the red,green and blue colors is: R:G:B=75:66:41=41%:36%:23%. That is, in thelatter case, the content of the blue color becomes bigger by about threetimes or more so that the relevant pixel seems to be a different color.

In case the gamma curve is deformed as shown in FIG. 5, thelow-proportioned color at the front side is increased at the lateralside. By contraries, the high-proportioned color at the front side isdecreased at the lateral side. In this way, the ratio of the red, greenand blue colors is approximated to each other. Consequently, the colorsviewed from the front side become reduced in the difference in the colorsensation when viewed from the lateral side. The colors become totallylight while being approximated to a white color, and this is called a“white-shift.” As a result, the color representation property becomesdeteriorated, and the picture image appears to be cloudy. The mostimportant cause of the white-shift is a deformation of the gamma curveat lower gray scales. When the deformation of the gamma curve is made athigher gray scales, it is extremely small. However, when the deformationof the gamma curve is made at lower gray scales of about 32 or less, thebrightness difference is about two times to ten times, and this makesthe white-shift appear serious.

FIG. 4 illustrates VT(Voltage-Transmittance) curves when a single domainvertically aligned liquid crystal cell is viewed from eight directions.

As shown in FIG. 4, the movement of the VT curve in a left directionwith lower gray scales is significantly made at a top side or at abottom side. At the left and right sides, the curve at the lower grayscales is elevated with the same outline as that at the front side. Atthe bottom-left side and the bottom-right side, the gray scale inversionis made early, and the VT curve again moves in the right direction whilebeing elevated. That is, the phenomenon where the gamma curve isdeformed upward with the lower gray scales becomes serious when thedirection of viewing the liquid crystal cell and the inclinationdirection of the liquid crystal molecule under the application of theelectric field are the same (when viewed from the head or tail of theliquid crystal molecule), but becomes negligible when those directionsare perpendicular to each other. Therefore, the gamma curve deformationat the left and right domains is important in viciously influencing theviewing angle based on the visibility at the left and right sides, andthe gamma curve deformation at the upper and lower domains is importantin viciously influencing the viewing angle based on the visibility atthe top and bottom sides. From the viewpoint of the user, the viewingangle at the left and right sides is more important than the viewingangle at the top and bottom sides. To compensate the gamma curvedeformation at the left and right domains that viciously influences theleft and right side visibility, the strength in the electric fieldwithin the left and right domains becomes weaker compared to that withinthe upper and lower domains. This will be now explained in detail.

FIG. 5 illustrates the VT curve at the front side of a single-domain VAcell where the rubbing is vertically made in an anti-parallel manner(the liquid crystal molecule being inclined up and downward), an averageVT curve at the left and right 60° sides thereof, an average VT curve atthe top and bottom 60° sides thereof, and a moved curve of the top andbottom average curve by about 0.3V.

As shown in FIG. 5, the VT curve at the left and right sides nearlycoincide with the VT curve at the front side with the lower gray scales,but the VT curve at the top and bottom sides begins to elevate at lowervoltages compared to the VT curve at the front side. That is, athreshold voltage (Vth) turns out to be lowered at the top and bottomsides, compared to that at the front side. However, when the VT curve atthe top and bottom side moves by about 0.3V, it nearly agrees with theVT curve at the front side with the lower gray scales. The fact that theVT curve at the top and bottom sides agrees with the VT curve at thefront side means that the visibility at the top and bottom sides issimilar to the visibility at the front side. Therefore, to control thevisibility at the left and right sides similar to the visibility at thefront side, the left and right side VT curves at the left and rightdomains may move by a predetermined voltage. The same effect as with themovement of the left and right side VT curve can be obtained in case theelectric field within the left and right domains is established to beweaker than the electric field within the upper and lower domains.

FIG. 6 is a plan view of a liquid crystal display having a thin filmtransistor array panel and a color filter panel according to a secondpreferred embodiment of the present invention, and FIG. 7 is a crosssectional view of the liquid crystal display taken along the VII/VII′line of FIG. 6.

As shown in FIGS. 6 and 7, in this preferred embodiment, othercomponents and structures of the liquid crystal display are the same asthose related to the first preferred embodiment except that a dielectriclayer 600 is formed on the first pixel electrode portion 91 withoutforming any slit there.

The effect of forming the dielectric layer 600 on the first pixelelectrode portion 91 is similar to that of forming slits at the firstpixel electrode portion 91. That is, the electric field within the leftand right domains is established to be weaker than that within the upperand lower domains. According to an embodiment of the present invention,the thickness of the dielectric layer 600 is preferably formed of about500 Å to about 1.5 μm.

FIG. 8 is a sectional view of a liquid crystal display according to athird preferred embodiment of the present invention.

As shown in FIG. 8, in this preferred embodiment, other components andstructures of the liquid crystal display are the same as those relatedto the first preferred embodiment except that a dielectric layer 600 isformed on the common electrode 400 while corresponding to the firstpixel electrode portion 91 without forming any slit at the first pixelelectrode portion 91.

The effect of forming the dielectric layer 600 on the common electrode400 is similar to that of forming the slits at the first pixel electrodeportion 91. That is, the electric field within the left and rightdomains is established to be weaker than that within the upper and lowerdomains.

FIG. 9 is a plan view of a liquid crystal display having a thin filmtransistor array panel and a color filter panel according to a fourthpreferred embodiment of the present invention, FIGS. 10 and 11 are crosssectional views of the thin film transistor array panel taken along theXI-XI′ line and the XII-XII′ line of FIG. 9, and FIG. 12 is an equationcircuit diagram of a liquid crystal display with the thin filmtransistor array panel shown in FIG. 9.

First, the thin film transistor array panel for the liquid crystaldisplay will be explained in detail.

A gate line assembly and storage capacitor lines 30 are formed at atransparent insulating substrate 10 such as glass.

The gate line assembly includes gate lines 20 extending in a horizontaldirection, and gate electrodes 21 protruded from the gate lines 20 upand downward.

The storage capacitor line 30 extends parallel to the gate line 20. Thestorage capacitor line 30 may have a branch line.

The gate line assembly and the storage capacitor line 30 are covered bya gate insulating layer 40, and a semiconductor layer 50 made ofamorphous silicon is formed on the gate insulating layer 40. Thesemiconductor layer 50 overlaps the gate electrode 21 to thereby form achannel portion for a thin film transistor. Ohmic contact layers 61, 62,and 63 made of amorphous silicon doped with n-type high concentrationimpurities such as phosphorous are formed on the semiconductor layer 50.

A data line assembly and connection electrodes 74 are formed on theohmic contact layers 61, 62, and 63 and the gate insulating layer 40.The data line assembly includes data lines 70 extending along thesemiconductor layer 50, source electrodes 71 connected to the data lines70, and first and second drain electrodes 72 and 73. The sourceelectrodes 71 protrude from the data lines 70 while being placed overthe gate electrodes 21. The first and the second drain electrodes 72 and73 are placed at both sides of the source electrode 71, respectively.The first and the second drain electrodes 72 and 73 are extended intofirst and second pixel regions around the gate line 20. The connectionelectrode 74 partially overlaps the storage capacitor line 30 whileelectro-magnetically interconnecting first and second pixel electrodes91 and 92 separated around the storage capacitor line 30. The ohmiccontact layers 61, 62, and 63 are located at the area where thesemiconductor layer 50 overlaps the data line assembly.

A protective layer 80 is formed on the data line assembly. Theprotective layer 80 has first and second contact holes 81 and 82exposing the one-sided ends of the first and second drain electrodes 72and 73, and a third contact hole 83 exposing the one-sided end of theconnection electrode 74.

First and second pixel electrodes 91 and 92 are formed on the protectivelayer 80 such that they are connected to the first and the second drainelectrodes 72 and 73 through the first and the second contact holes 81and 82. The second pixel electrode 92 is connected to the connectionelectrode 74 through the third contact hole 83. The first pixelelectrode 91 is overlapped with the connection electrode 74 while makingan electro-magnetic combination (capacitor-combination). The first andthe second pixel electrodes 91 and 92 are capacitor-combined with eachother by way of the connection electrode 74. The pixel electrodes 91 and92 are made of transparent conductive material such as indium tin oxide(ITO) and indium zinc oxide (IZO). Meanwhile, the first pixel electrode91 is provided with a plurality of horizontal opening portions 95extending in the horizontal direction. Vertical opening portions can beformed at the second pixel electrode 92. The occupation ratio of thefirst pixel electrode within one pixel region is preferably establishedto be about 30% to about 70%.

The electric potential of a common electrode (not shown) counter to thefirst and second pixel electrode 91 and 92 is usually applied to thestorage capacitor line 30.

In the meantime, the color filter panel is provided with a black matrix(not shown), color filters (not shown) and a common electrode (notshown). First to third opening portions 510, 520, and 530 are formed atthe common electrode. The first opening portion 510 extends in thevertical direction such that it bisects the second pixel electrode 92into left and right domains. The second and the third opening portions520 and 530 trisect the first pixel electrode 91 up and downward.Consequently, the first pixel electrode 91 are vertically partitionedinto four domains by way of the second and the third opening portions520 and 530, and the horizontal opening portion 95.

The connection electrode 74 is formed on the same plane as the data lineassembly having the data lines 70, the source electrode 71, and thefirst and second drain electrodes 72 and 73. Alternatively, theconnection electrode 74 may be formed on the same plane as the gate lineassembly having the gate lines 20 and the gate electrodes 21. In thelatter case, the storage capacitor line 30 should not overlap theconnection electrode 74.

The thin film transistor array panel is spaced apart from the colorfilter panel with a predetermined distance, and liquid crystal materialis injected between the two panels.

A compensation film (not shown) such as a biaxial film is attached tothe color filter panel. Two polarizing plates (not shown) are attachedto the outer surfaces of the thin film transistor array panel and thecolor filter panel, respectively.

As described above, two thin film transistors and two pixel electrodesare formed at one pixel region, and the two pixel electrodes at thepixel neighbors are capacitor-connected to each other by way of aconnection electrode. In this structure, excellent visibility can beobtained even when viewed from the left and right sides. This is becausethe voltage of the second pixel electrode 92 for the left and rightdomains is kept to be lower than the voltage of the first pixelelectrode 91 so that the electric field within the left and rightdomains is weaker than that within the upper and lower domains.

The reason that the voltage of the second pixel electrode 92 for theleft and right domains is kept to be lower than that of the first pixelelectrode 91 for the upper and lower domains will be now explained withreference to FIG. 12.

In FIG. 12, Clca indicates a liquid crystal capacitance formed betweenthe first pixel electrode 91 and the common electrode, Csta indicates astorage capacitance formed between the storage capacitor line 30 and thefirst pixel electrode P(n)−a, Clcb indicates a liquid crystalcapacitance formed between the second pixel electrode P(n)−b and thecommon electrode, Cstb indicates a storage capacitance formed betweenthe storage capacitor line 30 and the second pixel electrode P(n)−b, andCpp indicates a connection capacitance between the first pixel electrodeP(n)−a and the second pixel electrode P(n)−b.

As shown in FIG. 12, the first and the second thin film transistors areconnected to the same gate lines 20 and data lines 70, and the first andthe second pixel electrodes P(n)−a, and P(n)−b are connected to thefirst and the second thin film transistors, respectively. The first andthe second pixel electrodes P(n)−a, and P(n)−b make capacitor-connection(Cpp) with respect to each other while interposing the storage capacitorline 30 therebetween. In relation to one data line 70, when the nth gateline 20 becomes to be “on”, two thin film transistor (TFT) channelsbecome to be “on” so that voltage is applied to the first and the secondpixel electrodes P(n)−a, and P(n)−b, As the P(n)−b iscapacitor-connected to the P(n+1)-a, it is affected by the on-state ofthe latter. In this connection, the voltages of P(n)−a and P(n)−b can begiven by way of mathematical formulas 1 and 2.V[P(n)−a]=Vd(n)  (1)V[P(n)−b]=Vd(n)+[Vd(n+1)−V′d(n+1)]Cpp/(Clcb+Cstb+Cpp)  (2)

In the mathematical formulas 1 and 2, Vd(n) indicates a voltage appliedto the data line to drive the P(n) pixel, and Vd(n+1) indicates avoltage applied to the data line to drive the P(n+1) pixel, Furthermore,the V′d(n+1) indicates a voltage applied to the P(n+1) pixel at theprevious frame.

As expressed in the mathematical formulas 1 and 2, the voltage appliedto the P(n)−b pixel differs from the voltage applied to the P(n)−apixel, Particularly, in case dot inversion driving or line inversiondriving is made while the next pixel row expressing the same gray scaleas with the previous pixel row (practically, most of the pixels beingsimilar to this case), Vd(n)=−Vd(n+1), and Vd(n)=−Vd(n) (assuming thatthe common electrode voltage is the earth voltage). Therefore, themathematical formula 2 can be expressed by the following mathematicalformula 3:V[P(n)−b]=Vd(n)−2Vd(n)Cpp/(Clcb+Cstb+Cpp)=[(Clcb+Cstb−Cpp)/(Clcb+Cstb+Cpp)]Vd(n)=TVd(n)  (3)where T=(Clcb+Cstb−Cpp)/(Clcb+Cstb+Cpp).

It can be known from the mathematical formula 3 that the voltage appliedto the P(n)−b pixel is lower than that applied to the P(n)−a pixel. Thevalue of T is preferably established to be about 0.65 to about 0.95.

FIG. 13 is a plan view of a liquid crystal display according to a fifthpreferred embodiment of the present invention, and FIG. 14 is anequation circuit diagram of a liquid crystal display with the thin filmtransistor array panel shown in FIG. 13.

In this preferred embodiment, the thin film transistors and the pixelelectrodes at one pixel column are alternately connected to two datalines. That is, the thin film transistor and the two pixel electrodesP(n)−a, and P(n)−b at the P(n) pixel are connected to the m-th dataline, and the thin film transistor and the two pixel electrodes P(n)−a,and P(n)−b at the P(n+1) pixel are connected to the (m+1)-th data line.The detailed structure of each thin film transistor and pixel electrodeis the same as that related to the third preferred embodiment exceptthat the opening portions 95, 510, 520, and 530 are varied in theirpositions. That is, in the fourth preferred embodiment, the horizontalopening portion 95 is formed at the second pixel electrode 92. The firstopening portion 510 is formed at the first pixel electrode 91 whilebisecting the latter left and right, and the second and the thirdopening portions 520 and 530 are formed at the second pixel electrode 92while trisecting the latter up and down. Consequently, the first pixelelectrode 91 forms left and right domains, and the second pixelelectrode 92 forms upper and lower domains.

In the above structure, when the dot inversion driving is made, theelectric field within the left and right domains is kept to be weakerthan that within the upper and lower domains. That is, the electricpotential of the first pixel electrode 91 is constantly kept to be lowerthan that of the second pixel electrode 92 so that the visibility at theleft and right sides can be improved.

With the structure shown in FIG. 14, when the dot inversion driving ismade, the voltage of the same polarity is applied to the pixelelectrodes at the same pixel column so that the same effect as with thecolumn inversion driving is resulted. Therefore, in case the next pixelrow indicates the same gray scale as with the previous pixel row(practically, most of the pixels being similar to this case),Vd(n)=Vd(n+1), and Vd(n)=−V′d(n). Therefore, the mathematical formula 2can be expressed by the following mathematical formula 4:V[P(n)−b]=Vd(n)+2Vd(n)Cpp/(Clcb+Cstb+Cpp)=[(Clcb+Cstb+3Cpp)/(Clcb+Cstb+Cpp)]Vd(n)=TVd(n)  (4)where T=(Clcb+Cstb+3Cpp)/(Clcb+Cstb+Cpp).

In the mathematical formula 4, the voltage of the P(n)−b pixel is higherthan that of the P(n)−a pixel. Therefore, the electric field within theleft and right domains is constantly kept to be weaker than that withinthe upper and lower domains.

As described above the electric field at the left and right domains isconstantly kept to be weaker than the upper and lower domains so thatthe visibility at the left and right sides can be enhanced.

While the present invention has been described in detail with referenceto the preferred embodiments, those skilled in the art will appreciatethat various modifications and substitutions can be made thereto withoutdeparting from the spirit and scope of the present invention as setforth in the appended claims.

1. A liquid crystal display, comprising: a first substrate; a pluralityof pixels comprising a first pixel electrode and a second pixelelectrode disposed on the first substrate, wherein the first and secondpixel electrodes are disposed on the same layer, insulated from andpaired with each other to form a pixel; a second substrate facing thefirst substrate; and a liquid crystal layer interposed between the firstand second substrates, wherein the liquid crystal layer on each of thefirst pixel electrode and the second pixel electrode is divided by aplurality of domains, each of which are defined by a direction of liquidcrystal molecules when an electric field is applied to the first pixelelectrode and the second pixel electrode, and an electric field of thefirst electrode is different from an electric field of the secondelectrode, wherein the first pixel electrode is electrically connectedto a first conductive line with a first thin film transistor and thesecond pixel electrode is electrically connected to the first conductiveline with a second thin film transistor, and wherein the electric fieldof the first pixel electrode is different from the electric field of thesecond pixel electrode when the first thin film transistor and thesecond thin film transistor are off.
 2. The liquid crystal display ofclaim 1, wherein the first pixel electrode and the second pixelelectrode are paired at each side of the first conductive line.
 3. Theliquid crystal display of claim 1, further comprising a plurality ofsecond conductive lines, each of which are disposed between two adjacentfirst conductive lines.
 4. The liquid crystal display of claim 3,wherein a second conductive line is coupled with the first pixelelectrode in relation to capacitance.
 5. The liquid crystal display ofclaim 4, wherein the second conductive line is coupled with one of afirst pixel electrode and a second pixel electrode of a consecutivepixel in relation to capacitance.
 6. The liquid crystal display of claim3, wherein the first pixel electrode is overlapped by a portion of asecond conductive line.
 7. The liquid crystal display of claim 6,wherein the second pixel electrode is overlapped by a portion of asecond conductive line other than the second conductive line overlappedby the first pixel electrode.
 8. The liquid crystal display of claim 1,wherein the domains of the liquid crystal layer are divided by a domainpartitioning member.
 9. The liquid crystal display of claim 8, whereinthe domain partitioning member is formed on the first substrate.
 10. Theliquid crystal display of claim 8, wherein the domain partitioningmember is a plurality of slits of the first substrate.
 11. The liquidcrystal display of claim 10, wherein a width of the slits is about 2 μmto about 5 μm.
 12. The liquid crystal display of claim 1, wherein theliquid crystal molecules of a domain are initially aligned in a verticaldirection with the first substrate.
 13. The liquid crystal display ofclaim 12, wherein the domains of the liquid crystal layer are divided bya domain partitioning member.
 14. The liquid crystal display of claim13, wherein the domain partitioning member is formed on the firstsubstrate.
 15. The liquid crystal display of claim 14, wherein thedomain partitioning member is a plurality of slits of the first pixelelectrode.
 16. The liquid crystal display of claim 15, wherein a widthof the slits is about 2 μm to about 5 μm.
 17. The liquid crystal displayof claim 1, wherein a voltage of the first electrode is higher than avoltage of the second electrode.
 18. The liquid crystal display of claim1, further comprising a coupling electrode that makes an electric fieldof the first pixel electrode different from an electric field of thesecond pixel electrode contacting the first pixel electrode.
 19. Theliquid crystal display of claim 18, wherein the coupling electrodecontacts the first pixel electrode via a contact hole through aninsulating layer.
 20. The liquid crystal display of claim 19, wherein acoupling electrode is overlapped with a second pixel electrode via theinsulating layer.
 21. The liquid crystal display of claim 20, furthercomprising a plurality of second conductive lines, each of which aredisposed between two adjacent first conductive lines.
 22. The liquidcrystal display of claim 21, wherein a second conductive line is coupledwith the first pixel electrode in relation to capacitance.
 23. Theliquid crystal display of claim 22, wherein the second conductive lineis coupled with one of pixel electrodes of a consecutive pixel inrelation to capacitance.
 24. The liquid crystal display of claim 23,wherein the first pixel electrode is overlapped by a portion of a secondconductive line.
 25. The liquid crystal display of claim 24, wherein thearea of the first pixel electrode is occupied by about 30% to about 70%of the area of the first pixel electrode and the second pixel electrode.26. The liquid crystal display of claim 24, wherein the second pixelelectrode is overlapped by a portion of a second conductive line otherthan the second conductive line overlapped by the first pixel electrode.27. The liquid crystal display of claim 26, wherein the couplingelectrode is overlapped by the second conductive line.
 28. The liquidcrystal display of claim 26, wherein the area of the first pixelelectrode is different from the area of the second pixel electrode.